PMSM speed ramp input with V/f scalar control does not work

Hi,

I'm trying to implement a V/f scalar control for a PMSM, for speed step input there is no problem and the motor model works fine up until 2000 rpm more or less. But I want to set a reference speed that follows a ramp but somehow the motor becomes unstable way earlier than expected and the motor speed whas a different slope than the reference speed and I dont know why.

For instances this is the motor behavior under different speeds:

(also not sure why there are this huge speed drops at some step inputs)

And this is how it responds to a ramp input:

So, Why does the motor becomes unstable before thatn predicted when its subjected to a ramp input? Why does it have a different slope than the reference signal?

I have attached the simulink model along with the script that it is referenced to.

Answer 1

[Santiago Alfonso Ospina Botero]

I think I have a solution.

For some reason the back emf constant had to be a litle bit higher (k_bemf = 0.6 but previusly k_bemf =0.3). Dont know why but it worked just like that even tho the the previues value worked better since it provided less ripple and overshoot.

[Joel Van Sickel]

do you still have questions or are you happy with what you found?

[Santiago Alfonso Ospina Botero]

Well, the only thing that I dont understant is the diference in slope but other than that its all good! Thanks!